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The invention relates generally to client/server based computer systems and more particularly to the architecture of client/server based, network-coupled systems that are capable of providing multi-media displays including text, graphics, video, audio and scan converted radar on thin client displays. The invention also relates to the means by which multi-media and radar data are communicated between an application server computer and a thin client computer and how data are displayed on the thin client computer.
Computer system user interfaces have had several different architectures since their invention. Early computers used lights and buttons, or punch cards and printers to provide the user interface. Mainframe computers have traditionally used cathode ray tube (CRT) terminals that provided the user interface. The mainframe system was characterized by the fact that application programs run on the centralized computer housed in the computer center and users would interface to the computer via the display terminals and printers. A protocol was standardized for communication of output, or display commands and input or keyboard signals.
The invention of the personal computer changed the architecture to one where the computer processor and user interface devices were all highly integrated and co-located with the operator. The evolution of personal computers included the development of graphical user interfaces and pointing devices. The development of local area networks made it possible for many personal computers to share information easily in a distributed system. In many businesses, file server computers have been used to centralize the program and data storage. In this architecture, programs are downloaded from the file server to the desktop computer and executed. Data are often stored on the file server to allow easier system backups.
The continuing evolution of computer processing power and network bandwidth, combined with the increasing complexity of application software and operating systems has led to high system administration costs. The client/server system model using thin client displays is intended to reduce these rising costs and simplify system administration.
The client/server system architecture can be extended beyond the file server model to the application server model. The application server model is really a step back to the centralized mainframe system architecture except that the display terminals (thin clients) now provide a graphical user interface instead of just text and the mainframe is replaced by modern high performance application server computers. The communication between the client and server may be over phone lines, local area networks, or wide area networks.
The X windowing system was one of the first client/server display architectures, and is the dominant architecture on Unix-based operating systems. The objective of the X windowing system was to separate the processing of the user interface from the application program. The user interface is processed by a program called the X server which runs on the client processor. The application program, also called the X client, runs on an application processor. The X windowing system is most commonly used in distributed computing systems and it allows users to execute programs on a different computer than the operator interface computer. The X windowing system protocol for communication between the X client and the X server provides an efficient set of commands for exchanging display, keyboard and pointer actions.
A number of computer companies have developed competing protocols for exchanging display, keyboard and pointer actions. All share the same purpose of separating the computer running the application program from the computer performing the user interface functions.
The thin client system architectures that exist today have been focused on very low cost client hardware and low bandwidth network protocols. The primary applications include typical office uses such as database terminals, word processing, spread sheets and the like, that are characterized primarily by text and graphical content with fairly low rates of change. These systems benefit greatly from the reduced administration costs of the thin clients.
The benefits of the thin client architecture can also be extended to multi-media applications including radar display, video display and audio communication. Applications requiring these capabilities include military command and control systems, teleconferencing systems, interactive training systems, and even entertainment systems. These kinds of multi-media applications place increased demand on thin client computer systems because of the high bandwidth and processing load required to perform them. The present invention provides a solution to the problem of integrating multi-media capabilities into a thin client computing system.
Recent developments in digital television have resulted in several standards such as MPEG-1 and MPEG-2 from the Motion Pictures Experts Group that provide the means to compress digitized video so that it is feasible to transmit this data on a modern high performance digital network. Decompression of this video in a server before transmission to a client display is a problem because the bandwidth required for the decompressed data is very high. The decompression process may also require custom hardware to accomplish.
U.S. Pat. No. 5,923,285 entitled xe2x80x9cLow Bandwidth Digital Radar Video Distribution System,xe2x80x9d issued Jul. 13, 1999 to Martin J. Andrusiak, et al. describes a system architecture for distribution of digitized radar video on a modern computer network. This system architecture enables software scan conversion within a general purpose computer, by eliminating the need for dedicated hardware within the general purpose computer to capture and convert the radar video and azimuth signals from analog to digital form. It also improves the feasibility of software scan conversion within a general purpose computer because it substantially reduces the amount of data that needs to be processed for display.
U.S. Pat. No. 6,211,814 entitled xe2x80x9cMethod for Software Scan Conversion of Target Identification Data in a General Purpose Computer,xe2x80x9d issued Apr. 3, 2001 in the name of Scott J. Benjamin, et. al., describes a method for software based radar scan conversion that may be used for scan conversion in conjunction with the radar video distribution system of U.S. Pat. No. 5,923,285. The present invention enables the features of the scan conversion method of this application to be extended to thin client networks.
A radar scan conversion protocol is presented to allow thin client displays to perform radar scan conversion in conjunction with applications servers. The radar scan conversion protocol is defined such that the protocol information is in a compressed format which is expanded at the client for rendering of the radar display. This protocol may be implemented as an extension to a thin client protocol in order to pass radar video from the server to the client using minimal network bandwidth. In addition, the thin client may support communication of video and audio that may also be compressed (for transmission to the server) or decompressed (for display from the server) within the thin client. This thin client architecture is then capable of providing integrated graphics, radar, video and audio for military command and control, video conferencing, interactive training and entertainment (movies, radio) as well as general purpose computing.